United States Pharmacopeia (USP)

The United States Pharmacopeia is the official rulebook of drug quality in the United States — a thick reference that says, for each medicine, exactly what it must contain and how to prove it. Think of it as a recipe book combined with a test plan: anyone making a drug can look up the article and learn the standards it must meet.

USP is published together with the National Formulary (as USP-NF) by a non-governmental scientific organization, but its standards become legally enforceable in the US through the Federal Food, Drug, and Cosmetic Act. Each drug or excipient has a monograph listing identity, strength, purity, and the analytical methods used to verify them. General chapters describe shared procedures, such as the dissolution test or sterility test, that monographs refer to.

Other regions maintain their own compendia — the European Pharmacopoeia, the British Pharmacopoeia, the Japanese Pharmacopoeia — and harmonization efforts try to align them, but differences in methods and limits remain. A product can comply with USP yet still need to meet additional regulatory expectations beyond the compendium.